Code density is one factor in a tremendously complex system. The entire design philosophy of RISC architectures for the last 35+ years is predicated on the notion that it's not the most important one, and shouldn't be focused on in isolation.
From the abstract of the RISC-1 paper: "Although instructions are simpler, the average length
of programs was found not to exceed programs for DEC VAX
11 by more than a factor of 2."
